1. Field of the Invention
The present invention relates to a key structure, particularly to a key structure having a scissor-like linkage structure which is adapted for an electronic product with keys, such as a notebook computer, a computer keyboard, a telephone, a printer or a multi-function printer, for controlling key strokes.
2. Description of the Prior Art
Keyboards are widely used with various devices, such as computers, and notebooks, to input characters and numerals. Especially concerning notebooks, space is limited and the keyboard structure is particularly important. To make a key on the keyboard easy to depress, the key is usually designed with a scissors-like linkage structure (often called a support member) to function no matter where force is exerted on the key cap. In other words, even though the force is exerted on the edge of the key cap, the force is generally equally distributed over the entire surface of the key cap by the scissors-like linkage structure. Furthermore, while space is an especially important consideration in designing keyboards for portable computing devices, key switches with scissors-like linkage structure are often the solution.
Please refer to FIG. 1, which illustrates a perspective explored view of a key structure according to the prior art. The key structure has a key cap 90, a scissors-like linkage structure consisting of a first frame 91 and a second frame 92, and a base 93. The bottom ends of the first frame 91 and the second frame 92 are formed with pivots 94, 95 respectively for connecting pivotally with pivotal seats 96, 97 on the base 93. The top ends of the first frame 91 and the second frame 92 connect pivotally to the bottom surface of the key cap 90.
The first frame 91 and the second frame 92 are often formed by the injection molding technique. Connection mechanisms are provided on the middle portion of the first and second frames, so that the first and second frames are rotatably connected with each other to form the scissors-like linkage structure. However, in the conventional connection mechanism, the first frame and the second frame must be respectively formed on two independent areas during the injection molding process. Therefore, the necessary area for forming the scissors-like linkage structure is relatively large, resulting in an increase in manufacturing costs and the complication of the assembly of the inner and outer arms.
During the assembly of the scissors-like linkage structure, a step of separating the first frame and the second frame is performed first. Then, the two independent frames are sophisticatedly connected through the connection mechanism to form the scissors-like linkage structure. Therefore, the assembly process is relatively complicated and time-consuming, which induces the high assembly costs.
For solving the above-mentioned disadvantages, U.S. Pat. No. 6,706,986 published on Mar. 16, 2004 provides a scissors-like linkage structure for reducing injection molding costs and assembly costs. Please refer to FIG. 2, which shows a scissors-like linkage structure 70 applied in a key structure 60 for connecting a key cap 62 to a base 64 of the prior art. The scissors-like linkage structure 70 has a first frame 72 and a second frame 74. Each of the side arms of the second frame 74 are formed with a first hole 742 and a second hole 744 connecting to each other. Please refer to FIGS. 3A and 3B, which respectively illustrate a side view and a top view of the conventional scissors-like linkage structure. The scissors-like linkage structure is formed in a united manner by the injection molding technique. After injection, two pivots 720 of the first frame 72 are positioned in the first holes 742 of the second frame 74 and are moved along the radial direction. A space 700 is formed between the first frame 72 and the second frame 74, so that the second frame 74 can move in the first frame 72. The next step is moving the pivots 720 so that they hook into the second hole 744 and unite together. However, unavoidably, the scissors-like linkage structure of this prior art still needs one labor assembly step, which is pushing the pivots 720 of the first frame 72 into the second holes 744 of the second frame 74. Such step not only raises labor costs, but also increases the possibility of damage caused by improper assembly.
Moreover, the above mentioned scissors-like linkage structure 70 requires that the first hole 742 that is bigger than that of before, so that it increases the total height of the key structure and the height of the electronic device. It is therefore poorly designed for notebook computer keyboards.
Furthermore, the assembly action of the scissors-like linkage structure 70 pushing the first frame 72 into the second frame 74 results in a lateral force being applied to the pivots 720 of the first frame 72. The lateral force may cause the pivots 720 to break and raises the possibility of the product breaking down.
Besides, the scissors-like linkage structure 70 has the space 700 formed between first frame 72 and the second frame 74 let the second frame 74 move, so that the area of the mold of the scissors-like linkage structure 70 needs to be larger than the area of a mold of a single frame.
The inventor, after investigation and research, thus provides the present invention of logical design for reducing injection costs and reducing the number of assembly steps to overcome the above-mentioned imperfections.